There are two different methods for making panels which serve as background for the present invention, both of which result in a somewhat similar panel construction. The difference is that one method is capable of building into the panel more softness by including larger amounts of foamed material. Basically, this softer configuration is used in the more expensive luxury cars, whereas the other method is used basically in the large majority of other vehicles.
The method of making the luxury panel is essentially a two-stage process. In the first stage of the process, a substrate which is in the form of the panel is made by placing a fiberglass reinforcing mat in the lower half of a two-part mold and then filling the lower half of the mold with a foamable material such as liquid polyurethane capable of being cured into a foamed condition. After the foamable material has been inserted into the lower half of the mold, the upper half is moved down and then the foamable material is cured under heat to complete the substrate which is fairly rigid. In the second stage of the process, the substrate molded in the first stage is placed in the upper half of a second two-part mold. The lower part of the mold is in essence a vacuum mold. The second stage procedure is begun by moving a heated sheet of imperforate vinyl over the bottom part of the mold and then drawing by vacuum the heated sheet into the mold so that the three-dimensional configuration is formed on the vinyl. After the vinyl has been moved into engagement with the mold by the vacuum source, an amount of foamable material such as liquid polyurethane is then injected into the mold on top of the vinyl and thereafter the upper part of the mold which contains the substrate is then moved into cooperating relation with the lower part and the foamable material is cured into a relatively soft foamed condition.
The other more economical process is essentially a one-stage process which utilizes a two-part mold, the lower part of which again is a vacuum mold for the vinyl exterior sheet of the door panel to be made. In this case, the vinyl comes as the outer layer of a laminate which includes a layer of foamed material bonded thereto. The laminate is initially heated and then vacuum-drawn into the lower part of the mold. Next, a mat of fiberglass or similar reinforcing is placed inside the laminate vacuum adhered to the lower mold and, thereafter, a liquid polyurethane is added to the lower mold part over the vacuum-held laminate. The upper mold part is then closed and essentially a relatively rigid substrate is molded integrally with the vinyl laminate. In this process, it is not possible to provide much thickness and softness in the foam that is laminated with the vinyl or at least not as much as can be used in the second step of the two step process.
It is the usual practice to complete the final door panel molded in the mold assembly by thereafter adhering a carpet section to the lower planar exterior surface thereof. In the case of the two stage process, it has been a relatively simple matter to form the vacuum mold which receives the vinyl as a half mold in which the heated vinyl fills the mold and has its edges extending from the periphery of the mold surface along four sides and to mate this half mold with a full upper mold carrying a full substrate. In this way, it becomes possible to mold the short foamed polyurethane between the upper half of the substrate and the heated vinyl interfacing with the half mold. The resultant panel thus presented the lower half of the substrate without vinyl so that the carpet section could be added to complete the panel. Panels resulting from this modification of the basic two stage process have been used commercially for well over a year. The construction of the panel included a full relatively rigid substrate forming the entire interior surface of the panel, a carpet section adhered to the lower exterior surface of the substrate and an uneven thickness of foamed material bonded to the upper exterior surface of the substrate with vinyl material bonded to the uneven foamed material. To date, however, a comparable construction has never been made utilizing the more economical one stage method because of the necessity to provide full molds to mold a full substrate. Nevertheless, it is recognized that, if the vinyl and uniform layer of foamed material between the substrate and the carpet section could be eliminated in practicing the one stage method in a cost effective manner, the resultant product would likewise be more cost effective.